The present invention relates to hypodermic syringes and in particular to a hypodermic syringe for separately storing and mixing small amounts of two medicaments just prior to use.
Many drugs require mixing of powder and liquid immediately before injection into the patient. The constituents are generally separately stored and have to be measured and thereafter mixed prior to insertion into the syringe. Such a multi-step process is not only time consuming, but gives rise to improper measurement of the constituents, as well as to their possible contamination.
In U.S. Pat. No. 3,016,896 a syringe has been proposed in which a powder and liquid may be mixed within the syringe itself. In this patent the syringe is provided with two axially aligned barrel sections, the distal section being normally filled with powder and closed by the forward piston of a two piston plunger. The proximal barrel section is provided with an entrance port through which the liquid constituent of the drug can be eventually inserted as by the use of a second syringe. The forward piston of the plunger is then withdrawn from its seat into the proximal barrel section and the liquid and powder mixed, whereafter the syringe can be used in the conventional manner.
While the syringe suggested in U.S. Pat. 3,016,896 is capable of mixing powder and liquid within the syringe itself, it has several very distinctive disadvantages amongst which are the fact that the liquid and powder must be sequentially loaded into the syringe with the liquid last. The liquid has to be inserted through a hole extending radially into the barrel with the use of a separate syringe and since it is last to be loaded, the syringe itself cannot be used to measure or insure dosage. Further, the syringe must be taken apart completely in order for the powder to be inserted into the axially forward barrel, consequently neither ingredient can be stored in advance within the syringe. Further, dosage accuracy is subject to several errors in that filling the syringe with powder and thereafter with a liquid through a separate syringe can result in spillage, wastage, and thus inaccurate dosing. Still another major disadvantage of the syringe shown in the aforementioned patent is the fact that it cannot be safely filled with each of the constituents and stored for any appreciable length of time without the possibility of leakage between the barrel sections and with depression of the plunger so that premature mixing of the drug may occur during the transport from pharmacy and/or nurse's station to the patient.
It is the object of the present invention to provide a hypodermic syringe which permits stores albeit separately, liquid and powder constituents and permits their mixing just prior to use.
It is another object of the present invention to provide a syringe in which powder and liquid constituents can be stored safely over relatively long periods of time, without fear of mixing, and without fear of premature actuation of the plunger.
It is still a further object of the present invention to provide a hypodermic syringe which is adapted to quickly and easily prepare injectable material in fresh condition immediately prior to the injection thereof into the patient.
It is a further object of the present invention to provide a syringe which has means for storing a medicinal compound in powdered form and means for holding a suitable diluent or solvent for the powder separate from the latter until the same is desired to be mixed and injected into the patient.
The present invention has as a still further object the provision of a hypodermic syringe which is simple in construction and assembly, which is inexpensive to manufacture, and which is quite simple to use.
The foregoing objects together with other objects and further advantages of the present invention are evident from the following disclosure.